Metal arc lamp



H. STAMMREICH Oct. 20, 1931.

METAL ARG LAMP Original Filed July 13, 192B Patented Oct. 20, '1931 UNITED STATES.

PAJriazNT o1-'FICE mns srammnnron, or cnantor'rnnnune, NEAL BERLIN, ummm METAL no LAMP Original application illed July 13, 1928, Serial No. 292,348, and in Germany July 19, 1927. Divided and .this application led August 2, 1 930. Serial No. 472,578.

My present invention is a division of my.

copending application Serial No. 292,348; filed July 13, 1928 and concerns improvements in or relating to the operation of metal varc or metal vapour lamps. My invention has for its obj ect a method of operation avoiding certain disadvantages hitherto inherent to such lamps.

Metallic arcs have various advantages over thev ordinaryrcarbon arc and are primarily employed when a light rich in ultra-violet rays is desirable. The most usual form in this case is the mercury-quartz lamp which has the special advantage that no metal is consumed since the mercury distils and condenses inside the arc tube. y l

However, the energy distribution in the mercury spectrum is such that the light emitted cannot be employed for many purposes; thus it can in general not be considered for lighting purposes because it contains no red. Although its photo-chemical action is certainly considerable,-it is, however, extraordinarily decreased by the interpositi-on of glass in the path of the ray, the glass absorbing the greater part of the actinic rays located in the -short-wave ultra-violet range. For this reason many applications in photography, for example, are impossible.

y An attempt has been made, therefore, to employv in place of mercury metals the spectra of which appear to be especially favourable 'for the `particular purpose in question. Such attempts have, however, en-

countered technical diiculties caused by the Y fact that the metals, brought to melting or boiling by the arc, solidify at normal temperatures and either then and there or upon the lamp being set in operation afresh, burst, the housing. Furthermore, complications arise in connection with the striking of the are in the lamp, which, when mercury is employed may, due to its liquid nature, be effected merely by tipping.

In an attempt to avoid these difficulties, while retaining mercury as the lamp filling, other metal has been added thereto. Such amalgam lamps are, itis true, capable of operating, but do not fulfil the desired purpose, since due to the lower melting point of the mercury, almost exclusively the latter is vapourized in the are tube'and the spectrum of the added metal appears either not at all or very weakly only in comparison with the mercury spectrum.

The present invention makes it possible to use almost all metals in a glass or quartz lamp by employing as the filling in the manner of an amalgam lamp a liquid, pasty, or solid alloy, or a metal mixture, of such a l o.w melting pointthat'the lamp container cannot be destroyed, while the alloy or metal f mixture 1s, during the operation of the lamp,

An arc tube 1 has two branches 2 and 3 75 closed by means of quartz pieces 4 and 5 through which wires 6 and 7 for the electrical current are led. The quartz picces`4 and 5 tightly close the branches 2 and 3 so that the amalgam which is contained in two bodies Sand 9 in the branches 2 and 3 respectively may not flow out. The upper part of the arc tube 1 is connected to a receiver 11 by means of a bent conduit 10.

When the arcy irs struck at first only the low boiling mercury is vapourized by the arc and lows through conduit 10- to the receiver 11 where 4it is condensed. The are tube 1 being The operation of the lamp is as follows: S5

in 'communication with the receiver or con- 90 densatio'n chamber 11, the distillation of the metal does not-take place consequently, as in the previous lamps, Wholly inside the arc tube but the metal vapourized by the arc distils out of the tube and condenses and remains in the receiver. The size of this receiver preferably is such that it is capable of receiving exactly the amount of metal mercury to be removed from the arc tube while it causes or allows the other component metal to@ which is intended to form the arc and part of which may distil over during operation of the lamp to How back into the arc tube.

/After operation, the condensate collected in the receiver 11 is returned, by tipping, into the are tube where the original alloy then forms from the hot metals.

The lamp for carrying the invention into effect may be constructed in different ways.

The receiver may, forinstance, be provided with means connecting it to the arc tube otherwise than by conduit 1 I claim:-

The method of operating a metal are lamp, which comprises the steps of heatin a metal composition vand fractionally'distilling it, keeping one component distilled out of said metal composition, out of contact with the remainder of such composition during the operation of the arc lamp, and reuniting the components of said metal composition after the operation of the lamp.

In testimony` whereof I name to this specication.

HANN S STAMMRECH.

have signed my 

